DE1233316B - Process for establishing electrical contact between ceramic and metallic components - Google Patents

Description

Process for producing an electrical contact between ceramic and metallic components. The invention relates to a method of manufacture constant electrical contact between one with current passage on high Temperatures heatable refractory material and electrical connection parts. This task is of particular importance when using electric heating of rods made of refractory material, which are brought to red heat with the passage of electricity will. Known electrical connections consist of one on each end coiled metal wire. This arrangement works satisfactorily when the Stick ends protrude from the furnace wall and are cooled by air circulation can.

For other areas of application, such as the ignition of engines for aircraft, this arrangement is not useful because of the crowded A place for effective air cooling is not available and also the necessary It is not possible to seal the combustion chamber around the heating rods.

In addition, this application, which is mentioned as an example, results further difficulties due to the existing thermal stresses leading to mechanical Deformations can result, as well as due to chemical changes through education of insulating oxides on the contact surfaces.

The object of the invention is therefore to provide a method with your between a refractory component and metallic, electrical connection parts a mechanically strong connection with a good and stable electrical connection at the same time Contact can be established.

In order to provide ceramic tableware with gold or silver decoration, it is known to apply gold or silver powder with a viscous mass of dammar resin and turpentine oil to the ceramic and then to burn it in an oven. Instead of these precious metals can also. Aluminum powder can be used, for example when it comes to the manufacture of burned-in, shiny silver reflectors. Here, the aluminum powder in the form of a Aufschwernmung or a paste is - the subject is applied, and subsequently coated with glass enamel and the article is fired. These known methods always involve the creation of a decorative effect with the aid of metal dust embedded in an enamel coating or covered with a glaze. A mechanically strong and at the same time electrically conductive connection between metal and ceramic is not possible.

It is also a method of connecting metallic bodies to Bodies made of non-conductive material, e.g. B. ceramic bodies, known, wherein in one, With the exception of a ceramic body, a nietallic component is introduced and then is melted by an electric current until it is between the two parts existing play is eliminated by the molten body. With these procedures should be the usual cementing of the metallic component in an insulator, for example in the manufacture of spark plugs. Besides that this Measures require a high processing effort, there is also the There is a risk that the necessary pressure when upsetting the doughy State of heated metal part of the ceramic body bursts. According to another well-known It is suggested to provide ceramic material with a metallic coating, by putting metal powder in a liquid plastic and the mixture spreads on the ceramic material and then hardens the plastic. However, the use of this connection procedure is limited to such purposes where relatively low temperatures are expected and the one used for bonding Plastic does not age and become brittle due to excessive thermal stress.

In another known method for Hera place A vacuum-tight connection between ceramics and light metals is used as a bonding agent introduced a liquid metal component. Before pouring the liquid bonding metal the ceramic body must be provided with several specially selected layers of solder, that are vaporized and / or melted. This procedure is also conditional a very great effort, which is to be avoided according to the invention.

It is also known the conductivity of the connection points of radiators from silicon carbide by adding a liquid metal or another electrically conductive substance, preferably silicon, in direct contact is heated with the radiator so far above the melting temperature that a quick and even impregnation of the radiator part concerned takes place. This process concerns the manufacture of the radiator, but not the connection of power supplies.

Furthermore, a tubular heating rod has been described, the The glow part has a higher resistance than the connection ends, which are marked as Solid body trained inserts are provided, which are made of a material with low specific resistance and cemented into the pipe and through a subsequent annealing treatment are sintered together with the tube. The present However, the invention does not relate to the design of a heating rod itself, but rather on its connection to power supply lines.

It eventually became a contact device for rod-shaped electrodes proposed that one attached to the electrode head, adapted to the shape of the same Has contact plate made of highly heat-resistant material, the outer circumference of which is not is larger than that of the electrode. The electrode is rod-shaped and with a central one Provided bore, and the contact plate carries an anchor approach through which it is in the central hole of the heating rod with the interposition of an electrically conductive one Kitts is attached. With a putty that is used at room temperature, but naturally the electrical connection is not as good as with the method according to the invention characterized below, in which a metal powder is melted.

In contrast, the method according to the invention for production is distinguished constant electrical contact between one with current passage to one high temperature heatable refractory material and electrical connection parts characterized in that on the contact area between the refractory material and the Connection parts a known paste is applied, consisting of a Mixture of fat or resin and solvent with a metal powder, its melting point is considerably lower than that of the material forming the connecting parts, and the assembly thus formed is heated. This is preferably contained in the paste Metal aluminum powder, the key composition being 97% aluminum powder, 2% damar resin and 1% turpentine oil.

After the paste has been applied and the refractory material has been joined to the connecting parts, the heating should take place rapidly but steadily. The refractory material can be a rod or a rail, the ends of which are inserted into the connecting parts, in each of which there is a blind hole, the diameter of which is considerably larger than that of the rod or the rail. Silicon carbide is preferably used as the refractory material.

The inventive method enables that with the easily oxidizable Aluminum is a safe electrical and even with high thermal shock loads mechanical connection between metals and semiconducting refractory materials can be manufactured in a simple manner, and is not only for building space-saving Share for which it was designed, suitable but also general.

The invention is described below by way of example with reference to the drawing explained.

F i g. Fig. 1 shows a refractory rod, the ends of which are intended to receive metal end pieces, an end piece and part of the rod being shown in axial section; F i g. 2 shows the rod with the attached end pieces, partly in section.

In Fig. 1 shows a cylindrical rod 1 made of a refractory material with a certain electrical resistivity, e.g. B. silicon carbide, which is brought to a high temperature by the passage of current and is intended to cause the ignition of a fuel mixture, especially in the engine of an aircraft.

Metallic ends 2 and 3 are to be placed on the ends of the rod to establish the connection for supplying and removing the electrical current. These end pieces are simple cylindrical shells with relatively thick walls made of a refractory and non-oxidizable material when hot, e.g. B. a Bedin this cru, nts corresponding steel. The blind hole of each end piece has a diameter which, for. B. 1019 / o larger than that of the rod.

To establish permanent electrical contact between the heating rod 1 and the metallic end pieces 2 and 3 , the following procedure is used: A very fine powder of a metal or a conductive metalloid is produced with a melting point which is considerably lower than that of the material forming the end pieces . Aluminum powder can be used for this.

This powder is intimately neutralized with an optionally Fat, e.g. B. tallow, glycerine, dammar resin, etc., and a solvent mixed, e.g. B. ordinary gasoline> turpentine oil or something known as white-spirit Substitute product until the mass takes on the texture of fresh putty.

After the powder has been brought into the form of a plastic mass by means of a binder, the two ends of the rod 1 are smeared with this paste, as at 4 and 4 'in FIG. 1 shown. Furthermore, this paste is brought into the bores of the metallic end pieces, as shown at 5 in the drawing.

The end pieces 2 and 3 are then placed on the rod 1 (FIG. 2). The excess paste is removed and the assembly is exposed to rapidly but steadily increasing current passage. The rod is finally made to glow by the heat of the current. Under the action of heat, the metal or the metalloid of the paste melts, while certain constituents which were used to produce the paste evaporate or react. When the smoke has stopped, the process is over. After cooling, the rod 1 and its end pieces 2 and 3 adhere perfectly to one another, pressure phenomena resulting from the expansion during heating and the contraction during cooling contribute to the strength of the arrangement thus produced. Element can then be installed in any spark plug. The electrical contact established between the rod and the end pieces according to the above method is permanent and has a durability which ensures a high level of ignition reliability.

The following composition, given as an example, has given very good results: Aluminum powder ................. 9711 / o Dammar resin . .................... 2% Oil of turpentine ...................... 10/0 This binding agent is sufficiently flexible to compensate for possible expansion. It also prevents contact with the air which causes the formation of insulating oxides.

The invention can of course be modified. So can warming the arrangement for producing the firm connection of the paste with the end pieces and the rod are generated by a heat source other than heat from electricity. One can z. B. heat the assembly in a furnace or by means of a welding torch.

Claims (2)

Claims: 1. A method for producing a permanent electrical contact between a refractory material that can be heated to high temperatures with current passage and electrical connection parts, characterized in that a paste known per se is applied to the contact area between the refractory material and the connection parts, consisting of a Mixture of fat or resin and solvent with a metal powder, the melting point of which is considerably lower than that of the material forming the connecting parts, and the arrangement thus formed is heated. 2. The method according to claim 1, characterized in that the metal contained in the paste is aluminum powder. 3. The method according to claim 2, characterized in that the paste contains 97% aluminum powder, 211 / o Dammar resin and 1% turpentine oil. 4. The method according spoke 1 to 3, characterized in that the heating is carried out rapidly but steadily increasing. 5. The method according to claim 1 to 4, characterized in that the refractory material is a rod or a rail, the ends of which are inserted into metallic, cylindrical connecting parts with a blind hole, the diameter of which is considerably larger than that of the rod or the rail. 6. The method according spoke 5, characterized in that the ends of the rod or the rail and the bores of the connecting parts are coated or lined with paste prior to joining. 7. The method according spoke 1 to 6, characterized in that silicon carbide is used as the refractory material for the rod to be heated. Considered publications: German Patent Nos. 945 473, 972 452, 630 402, 587 651; German Auslegeschrift No. 1 011089; Austrian Patent No. 150,373; British Patent No. 490 232; Machis, "Metallische Überzüge", p. 18; Consultation room for ceramics, glass and enamel, 1951, p.127.